Method and apparatus for bleaching pulp



New. 5, 1929. A. 1:). MERRILL -fi METHOD AND APPARATUS FOR BLEACHING PULP Filed Aug. 11, 1925 2 Sheets-Sheet 1 III INVENTOR ATTORNEY Nov. 5, 1929.

A. D. MERRILL METHOT AND APPARATUS FOR BLEACHING PULP Filed Aug. 11, 1925 2 Sheets-Sheet 2 l N VEN TOE.

Patented Nov. 5, 1929 UNITED STAT S PATENT Faisal? ALBERT D. MERRILL, 0F WATERTOWN, NEW YORK, ASSIGNOR, BY MESNE ASSIGN- MENTS TO THE INTERNATIONAL BLEACHING CORPORATION, A CORPORATION OF DELAWARE METHOD AND APPARATUS FOR BLEACHING PULP.

Application filed August 11, 1925. Serial No. 49,635.

My invention relates to pulp cellulose, paper stock fiber, and kindred material bleaching apparatus, and to a method of carrying out said bleaching in said apparatus, in a cheap, simple and highly efficient manner. In my system, I use a minimum amount of bleaching. fluid, a minimum amount of steam, and bleach thoroughly in a time saving operation, mixing the bleach agent thoroughly with the stock, so that all the fibers and parts of the stock are bleached evenly and uniformly, without destroying the texture of the fibers, or destroying or impairing their vitality.

In carrying out my method of bleaching pulp, I place the requisite amount of stock in the cell or tank together with the bleaching agent.

In the tank I arrange a ribbon agitator, on a shaft, which, when rotated or revolved, carries the ribbon agitator around with it and on this shaft I also place a worm kneader element.

The ribbon agitator raises the stock on the outer side of the mass while theworm kneader forces said stock down the central portion of the mass. 1 g

The ribbon elevator or agitator stirs the stock up very thoroughly and at the same time the worm kneader kneads or presses the particles of the stock together and forces them down to the bottom of the tank from which they are again lifted by the ribbon elevator or agitator. This continuous up:- ward and downward working of the stoc intermixes it with the bleaching liquor so thoroughly that all the fibers in the stock come directly under the bleaching treatment quickly and completely, insuring standard uniformity. By reason of these conditions no direct steam is added, for under the con- .tinued action of this up and down movement of the pulp, and the high consistancies employed, no extra heat is required over the natural heat of the surrounding air;

It will readily be understood that by reason of this operation, the bleaching can be done rapidly, as by the down movement of the stock, and further by reason of the worm kneader squeezing and pressing said stock, the bleaching liquor is forced to penetrate and permeate said stock and thus the bleaching operation is materially assisted, and time is saved without detracting from the thorough- 'ness of the bleaching effect.

0 One of the main objects of this invention is to provide a system to handle pulp in dense form, even to a greater degree than it is now handled in such form, or has been handled'heretofore.

By handling a dense mass of pulp and thoroughly bleaching the same, time is saved and the bleaching can be done more uniformly and thoroughly. I 1 By the use of my method and apparatus, I am enabled to handle stock which is practically dry, before the addition of the bleaching agent, thereby being enabled to remove a larger proportion of the dirt, shortening'the bleaching time, and cutting down the bleach consumption. My system will handle all densities of stock from 30% to 90% bone dry i. e. stock having 90% of fibre and 10% water or other liquid. Such stock known to the trade as air dry stock. From actual tests, however, and for economical reasons, I would rather handle pulp not over 60%, say from 35 to 60%. 7

It will be seen that the oonvolutions which make up the ribbon elevator and agitator, for carrying the pulp up on the outside, that is, near the bowl wall, are of a gradual and special pitch, thus said ribbon agitator and elevator can perform the duty of raising and agitating pulp of a heavy density, e11- abling me to work pulp or stock "of said density before referred to, to wit: 35 to 60% and even more; and it will be further noted that the more dense the pulp the better the is commonly I .erate, thereby insuring thorough mixture and quick action, enhancing the appearance of the bleached stock and saving time and money..

During the bleaching operation, I use a temperature not exceeding 25 C.

In the accompanying drawings, forming part of this specification Fig. 1, is a section of my apparatus taken on the line 11 of Fig. 2, parts being in section and other parts in elevation and in full lines,

Fig. 2, is a plan view of the apparatus, and

Fig. 3, is a plan view of the bottom of the tank. y

In the drawing 1 represents a tank, cell or receptacle, for holding the stock, and on the inside is usually made in bowl shape as shown, and of a concrete construction 2, on the outside, the bowl being marked 3. The bowl can be lined with white tile, if desired, but lining is not absolutely necessary for the proper operation of the apparatus. For the purpose of description I will call the bowl and concrete, the tank, as this is the usual name iven to the holder of the stock. Any kind 0 covering may be used with the tank. The tank is supported on a frame work or base 4.

The bottom of the tank is made upof an iron casting 5, which has a recess 6 molded in same, fora stuffing gland as 7 I provide a water connection 8, in order to dilute the stock after bleaching, so that the same can be emptied through the dumping valve 9, operated through the agency of valve shaft 10 and wheel 12. I

I provide a shaft 13, which is connected to the worm speed transformer 14, operated by a motor 15, and this shaft rotates the spiral ribbon conveyor and agitator 16 and the worm kneader 17; both being located on this same shaft, however, the wgrm kneader being designed to force the stock down the center while the ribbon agitator elevates the stock on the outside as shown.

A number of brace arms 18 support the ribbon agitator on the shaft 13. The ribbon agitator 16 and the worm kneader 17 may be supported in the tank in any desired man ner:

In operation, the ribbon agitator 16 revolves as the shaftrotates in the direction shown by the arrow, and thus lifts the stock up and turns it over until it is engaged by' the worm conveyer or kneader 17, where the stock is kneaded and forced down to the bot- I have drawn a dotted line 19 showing the forced downward by the kneader worm. This space is marked and is between the line 19, and the top of the tank. Although the ribbon agitator and elevator and the kneader worm ,are on the same shaft, they operate op-' positely as heretofore set forth. Ido not confine myself to the exact contour of the ribbon agitator and the worm kneader, nor 1 do I confine myself to the exact construction and operation herein shown and described, but may modify and change the-same, just so that such changes and modifications iall within the scope of this specification and claims. 4

What I claim as, new and my invention and desire to secure by Letters Patent is:

1. In pulp bleaching, the method of moving a mass of pulp and bleaching agent, by imparting to the outside of said mass an upward movement, turning the same over toward the center of the mass and allowing the same to fall by gravity toward said center, then forcing the same downward at the center, toward the bottom of the mass.

2. In pulp bleaching, the method of moving a mass of pulp and bleaching agent, by imparting to the outside of said mass an upward movement, turning the same over toward the center of the mass and allowing the same to fallby gravity toward said center, then forcing the same downward at the center toward the bottom of the mass, and kneading the mass while forcing the same downwardly.

3., In'pulp bleaching, the method of moving a mass of pulp having a density of over thirty but not greater than ninety per cent, and bleaching agent, by imparting to the outside of said mass an upward movement, turning the same over toward the center of the mass and allowing the same to fall by gravity toward said center, then forcing the same downwardly at the center toward the bottom of the mass.

4. In pulp bleaching, the method of moving a mass of pulp and bleaching agent having a density of over thirty per cent and up to sixtv per centafter adding bleaching agent, y imparting to the outside of said mass an upward movement, turning the same over toward the center of the mass and allowing the same to fall by gravity toward said center, then forcing the same downward at the center toward the bottom of the mass.

5. In pulp bleaching, the method of moving a mass of pulp and bleaching agent, by imparting to the outside of said mass an upover toward the center of the mass, and falling by gravity toward and down to the center of the mass, then forcing the same downwardly at said center, and kneading the same downwardly at said center, and repeating said operations.

7. In pulp bleaching, the method of moving a mass of pulp and bleaching agent by imparting to the outside of said mass, an upwardly travelling movement, imparting a downward movement to the central portion of the mass, so as to maintain a cavity in the upper portion of the mass, and allowing the pulp to fall by gravity from the out' side downwardly into said cavity.

8. In pulp bleaching, the method of moving a mass of pulp and bleaching agent by imparting to the outside of said mass, an upwardly travelling movement, imparting a downward movement to the central portion of the mass, so as to maintain a flaring cavity in the upper central portion of the mass, allowing the pulp to fall by gravity from the outside of the mass into said cavity, and kneading the central portion of the mass as it moves downwardly.

9. In pulp bleaching, elevating the outside portion of a mass of pulp while agitating the latter, causing the pulp to fall by gravity from the upper part of its outer portion toward the central portion of .the mass, the concentration of the pulp being such as to provide a non-fluid mass.

10. A method of bleaching a mass of pulp of a heavy density by moving the same and a bleaching agent in an upward spiral path at the outside of said mass and by moving said mass downwardly, approximately in a vertical line, in the center of the mass.

11. A method of bleaching pulp of a density over thirty per cent, but not greater than ninety per cent, by moving the same in and upward spiral path at the outside .of said mass and by moving said mass downward approximately-in a vertical line at the center of the mass.

12. A method of agitating pulp of a density from thirty to sixty per cent, by moving same in an upward, approximately vertical line, on the outside of said mass, and moving said mass downward, approximately in a vertical line at the center of the mass.

13. A method of bleaching pulp, which comprises mixing the pulp with a bleaching agent, the concentration of the pulp being more than thirty per cent but not greater than ninety per cent and subjecting the same to a temperature not exceeding 25 C.

14. An apparatus for bleaching pulp, comprising a tank, a vertical rotary shaft arranged in the tank, a spiral ribbon conveyor and agitator mounted on the shaft and arranged in close proximity to the inner surface of the tank, one end of the conveyor being positioned at a greater distance from the shaft than the other end of the conveyor.

15. A pulp bleaching apparatus, comprising a tank having a substantially parabolic inner surface, a rotatable shaft arranged in the tank, and a spiral rubbon conveyor mounted on the shaft and arranged in close proximity to said inner surface, said conyeyor conforming to the shape of said surace.

16. An apparatus for use in bleaching pulp comprising a tank, a vertical rotatable shaft arranged in the tank, a spiral ribbon conveyor mounted on the shaftand arranged in close proximity tothe inner surface of the tank, and adapted to elevate and agitate the outer portion of a mass of pulp, and a kneader fixed'to the shaft and arranged within the conveyor for forcing the central portion of the mass downwardly.

17. A pulp bleaching apparatus, comprising an open tank having the inner surface of its bottom curved, a vertically disposed rotatable shaft arranged in the tank, a spiral ribbon conveyor and agitator mounted on the shaft and arranged in close proximity to the inner surface of the tank, and a kneader mounted'on the shaft and arranged within said conveyor.

18. A pulp bleaching apparatus, including a tank having a bowl-shaped inner surface, a vertically disposed' rotatable shaft arranged in the tank, a spiral ribbon conveyor and agitator mounted on the shaft and conforming to the shape of the inner surface of the tank, the upper end of the ribbon 'conveyor being arranged at a greater distance from the shaft than the'lower end of the 1 same.

19. A pulpbleaching apparatus, including a tank having a bowl-shaped inner surface, a vertically disposed rotatable shaft arranged in the tank, a spiral ribbon conveyor and agitator mounted on the,shaft and conforming to the shape of the inner surface of the tank, the'upper end of the ribbon conveyor being arranged at a greater distance from the shaft than the lower end of the same, and a kneader mounted oh the shaft near the bottom of the tank and shaft to force material elevated by the conveyor downwardly.

20. A method of agitating and kneading pulp stock of a density from 30 to 90% with a bleaching reagent, subjecting the pulp agitation and'kneadin rapidly and inv such a manner that all partlcles of the pulp mass are in constant motion.

21. In pulp bleaching, the method of 100s- 5 ening a, pulp mass of between 30% and 90% consistency and bleaching agent, and then pressing the pulp mass and bleaching agent together again and repeating said operation. In testimony whereof, I aflix my signature at lVatertown, New York, this thirty-first day of July, 1925.

ALBERT D. MERRILL. 

